This invention relates to stain resistant polymeric compositions for the treatment of natural and synthetic fibers.
Nylon has had a dramatic effect on both industry and society since its discovery by W. H. Carothers more than fifty years ago. It is estimated that 75% of all carpet currently produced in the United States, and 46% of all carpet produced in Europe, is prepared from nylon fiber.
Nylon fiber is relatively inexpensive and offers a combination of desirable qualities such as comfort, warmth, and ease of manufacture into a broad range of colors, patterns and textures. However, nylon, as well as other polyamide fibers and fabrics, is easily stained by certain natural and artificial colorants such as those found in coffee, mustard, wine, and soft drinks.
Recently, fluorochemical coatings have been developed that prevent wetting of the carpet surface, by minimizing chemical contact between the carpet surface and substances that can stain the carpet, making the substance easier to remove. Fluorochemicals also provide a physical barrier to staining material. Examples of commercially available fluorochemical coatings include Scotchgard.TM. 358 and 352 (Minnesota Mining & Mfg. Co.) and Zepel.TM. and Teflon.TM. (E. I. Du Pont Nemours & Co.). Antron Plus.TM. carpet manufactured by Du Pont contains nylon carpet fibers coated with fluorocarbons.
While fluorochemical coatings are effective in protecting carpet from substances such as soil, they offer little protection from stains resulting from acid dyes that are found in common household materials such as wine, mustard and soft drinks. Acid dyes are bases that bond to protonated amino sites in the polyamide fiber. A wide variety of methods have been developed to make polyamide fibers or other fibers with terminal amino groups more resistant to staining by acid dyes. The most widely used method involves the application to the polyamide fiber of a formaldehyde phenol or naphthol condensation polymer that has sulfonate groups on the aromatic rings. The sulfonate and hydroxyl groups ionically bond to available protonated amino groups in the polyamide fiber, preventing the protonated amino groups from later bonding to common household acid dyes. The polymeric coating also protects the carpet fiber by creating a barrier of negative electric charge at the surface of the fiber that prevents like-charged acid dyes from penetrating the fiber.
Examples of phenol-formaldehyde condensation polymers are described in U.S. Pat. No. 4,501,591 to Ucci, et al., and U.S. Pat. Nos. 4,592,940 and 4,680,212 to Blythe, et al. In particular, U.S. Pat. Nos. 4,592,940 and 4,680,212 describe a formaldehyde condensation product formed from a mixture of sulfonated dihydroxydiphenylsulfone and phenylsulphonic acid, wherein at least 40% of the repeating units contain an --SO.sub.3 X radical, and at least 40% of the repeating units are dihydroxydiphenylsulfone.
Sulfonated hydroxyaromatic formaldehyde condensation products marketed as stain resistant agents include Erional.TM. NW (Ciba-Geigy Limited, containing a formaldehyde condensation copolymer of dihydroxydiphenylsulfone and naphthalene sulfonic acid), Intratex N.TM. (Crompton & Knowles Corp.), Mesitol.TM. NBS (Mobay Corporation), FX-369 (Minnesota Mining & Mfg. Co.), CB-130 (Grifftex Corp.), and Nylofixan P (Sandoz Chemical Corp., containing a formaldehyde condensation copolymer of dihydroxydiphenylsulfone and 2,4-dimethylbenzenesulfonic acid). Antron Stainmaster.TM. carpet manufactured by Du Pont contains nylon fibers that have both a fluorocarbon coating and a sulfonated phenol-formaldehyde condensation polymeric coating.
While sulfonated hydroxyaromatic formaldehyde condensation polymeric coatings reduce the staining of polyamide fibers by acid dyes, they do not impart resistance to staining by compounds such as mustard with tumeric or hot coffee. Further, ultraviolet light and nitrogen dioxide can yellow the polymers over time. The yellowing can be severe enough to prevent the use of the stain resistant compositions on light shaded textile articles.
Efforts to overcome the discoloration problem are discussed in U.S. Pat. No. 4,780,099 to Greschler, et al., describing the reduction of yellowing by application of phenol formaldehyde condensation stain resistant compositions at pH values of 1.5-2.5, and in European Patent Application 87301180.3 by E. I. Du Pont Nemours & Co., describing that polyamide fabrics with improved resistance to staining as well as discoloration prepared with etherified or acylated formaldehyde phenol condensation polymers. U.S. Pat. No. 4,822,373 to Olson et al. discloses a stain resisting composition for nylon fibers prepared by blending a partially sulfonated novolak resin with a homopolymer of methacrylic acid or a copolymer of methacrylic acid with another ethylenically unsaturated monomer. U.S. Pat. No. 4,937,123 to Chang et al. discloses a stain resistant composition for nylon fibers that includes a homopolymer of methacrylic acid or a copolymer of at least 30% methacrylic acid with another ethylenically unsaturated monomer.
U.S. Pat. No. 4,940,757 and U.S. Pat. No. 5,061,763 to Moss, et al., disclose a stain resistant composition prepared by polymerizing an .alpha.-substituted acrylic acid in the presence of a sulfonated aromatic formaldehyde condensation polymer using a free radical generating agent. The resulting product imparts to polyamides improved resistance to acid dyes, while exhibiting little discoloration over time, and can be used at levels of application less than other compositions that are composed of a mere blend of polymethacrylic acid and a sulfonated aromatic formaldehyde condensation polymer.
While the above-described stain resistant compositions impart a degree of protection to polyamide fibers, many of them are colored solutions that actually alter the color of the fiber upon application. For example, when a yellow or amber solution is applied to a blue fiber, the fiber can acquire a greenish tint.
Given the tremendous volume of polyamide fiber used domestically and commercially world-wide, there is a need to provide still improved stain resistant compositions that offer a suitable combination of protection from staining by common products such as mustard, coffee, and soft drinks, that do not discolor over time, and that are economical to produce. There is also a need to provide a stain resistant composition that is sufficiently colorless that it does not alter the tint of the dyed fiber.
It is therefore an object of the present invention to provide a composition that imparts protection from staining to polyamide textile and carpet products.
It is another object of the present invention to provide a stain resistant composition that is sufficiently colorless that it does not significantly alter the tint of the fiber upon application.
It is a further object of the present invention to provide a stain resistant composition that does not yellow significantly over time.
It is still another object of the present invention to provide methods for coating natural and synthetic fibers that are effective, versatile, economical and result in products that are resistant to staining by many common household compounds, including coffee, mustard, wine and soft drinks.
It is a still further object of the present invention to provide natural and synthetic fibers coated with these stain resistant compositions that do not discolor significantly over time.
It is yet another object of the present invention to provide a method for preparing a stain resistant composition.